Method and apparatus for cooling a semiconductor device

ABSTRACT

A method and an apparatus for cooling a semiconductor device. The method comprises the steps of contacting a surface of the semiconductor device with respective end portions of an array of contact elements thermally coupled to a cooling fluid, and disposing a flexible, heat conductive sheet between the respective end portions of the contact elements and the surface of the semiconductor device for transferring heat generated in the semiconductor device to the cooling fluid via the sheet and the contact elements.

FIELD OF INVENTION

The present invention relates broadly to a method and an apparatus forcooling a semiconductor device.

BACKGROUND

During electrical testing of a semiconductor device, an electric currentmay be supplied to relevant components of the semiconductor device undertest. With increasing metal layers and flip chip bonding, analysis ofthe integrated circuits (IC) on the semiconductor device can typicallyonly be done from the backside of the chip through the silicon substrateusing infrared imaging. It has been noted that the semiconductor devicemay heat up during such testing due to power dissipation and may need tobe cooled. In one existing cooling method, a cooled diamond window isused to press on the backside of the semiconductor device. This methodallows air-gap lens operation. The diamond window allows the system toperform the analysis through the silicon substrate while testing. Thediamond conducts heat from the semiconductor device to an attachedcopper heat exchanger block. Typically, the heat exchanger uses a cooledliquid or super cooled air. Another version of this method involveshaving a small opening on the diamond window to allow a Solid ImmersionLens (SIL), which can enhance the imaging resolution, to land on thedevice.

However, in the above method, the thermal resistance is high between thecold contact (diamond window) and the semiconductor device, and betweenthe cold contact and the heat exchanger block, making it difficult forthe user to operate the device at a higher power. In addition, in theabove method, device planarity requirements are typically stringent, andpassive components protruding from the device may have to be removed. Inanother existing cooling method, a liquid jet is used to spray a cooledliquid onto the silicon substrate of the semiconductor device. Thesprayed liquid is then collected back to the heat exchanger. However,this method typically can only be used with an SIL which has sealedoptics. Also, this method can only cool the device to temperatures above10 degrees Celsius (° C.).

A need therefore exists to provide a method and an apparatus for coolinga semiconductor device that seek to address at least some of the aboveproblems.

SUMMARY

In accordance with a first aspect of the present invention there isprovided a method for cooling a semiconductor device, the methodcomprising the steps of contacting a surface of the semiconductor devicewith respective end portions of an array of contact elements thermallycoupled to a cooling fluid, and disposing a flexible, heat conductivesheet between the respective end portions of the contact elements andthe surface of the semiconductor device for transferring heat generatedin the semiconductor device to the cooling fluid via the sheet and thecontact elements.

In accordance with a second aspect of the present invention there isprovided an apparatus for cooling a semiconductor device, comprising achamber configured for receiving a cooling fluid, an array of contactelements configured to be thermally coupled to the cooling fluid, and aflexible, heat conductive sheet disposed at respective end portions ofthe contact elements, such that, in operation, the sheet is disposedbetween the respective end portions of the contact elements and thesurface of the semiconductor device for transferring heat generated inthe semiconductor device to the cooling fluid via the sheet and thecontact elements.

In accordance with a third aspect of the present invention there isprovided an method for cooling a semiconductor device, the methodcomprising the steps of contacting a surface of the semiconductor devicewith an end portion of a contact element thermally coupled to a coolingfluid, and disposing a flexible, heat conductive sheet between the endportion of the contact element and the surface of the semiconductordevice for transferring heat generated in the semiconductor device tothe cooling fluid via the sheet and the contact element.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be better understood and readilyapparent to one of ordinary skill in the art from the following writtendescription, by way of example only, and in conjunction with thedrawings, in which:

FIG. 1( a) shows a perspective view of a cooling apparatus according toan example embodiment.

FIG. 1( b) shows an alternative perspective view of the coolingapparatus of FIG. 1( a).

FIG. 1( c) shows a side view of the cooling apparatus of FIG. 1( a).

FIG. 1( d) shows a cross-sectional view of the cooling apparatus about aline A-A in

FIG. 1( c) according to an example embodiment.

FIG. 2( a) shows an enlarged view of detail B in FIG. 1( d).

FIG. 2( b) shows an enlarged view of detail C in FIG. 1( d).

FIG. 3( a) shows a perspective view of a cooling apparatus according toan alternate embodiment.

FIG. 3( b) shows an alternative perspective view of the coolingapparatus of FIG. 3( a).

FIG. 3( c) shows a side view of the cooling apparatus of FIG. 3( a).

FIG. 4( a) shows a cross-sectional view of the cooling apparatus of FIG.3( a) according to an example embodiment.

FIG. 4( b) shows an enlarged view of a center contact in detail B ofFIG. 4( a).

FIG. 4( c) shows an enlarged view of contact elements in detail C ofFIG. 4( a).

FIG. 5( a) shows a perspective view of the center contact of FIG. 4( b)according to an example embodiment.

FIG. 5( b) shows a side view of the center contact of FIG. 5( a).

FIG. 6( a) shows a perspective view of the contact element of FIG. 4( c)according to an example embodiment.

FIG. 6( b) shows a side view of the contact element of FIG. 6( a).

FIG. 7 shows an exploded perspective view of a cooling apparatusaccording to another embodiment.

FIG. 8 shows an exploded perspective view of a system for inspecting asemiconductor device according to an example embodiment.

FIG. 9( a) shows a perspective view of the system of FIG. 8 when the SILassembly is in contact with the cooling apparatus.

FIG. 9( b) shows a side view of the system of FIG. 9( a).

FIG. 9( c) shows a cross-sectional view of the system of FIG. 9( a).

FIG. 10 shows a flow chart illustrating a method for cooling asemiconductor device according to an example embodiment.

DETAILED DESCRIPTION

FIG. 1( a) shows a perspective view of a cooling apparatus 100 accordingto an example embodiment. FIG. 1( b) shows an alternative perspectiveview of the cooling apparatus 100 of FIG. 1( a). FIG. 1( c) shows a sideview of the cooling apparatus 100 of FIG. 1(a). FIG. 1( d) shows across-sectional view of the cooling apparatus 100 about a line A-A inFIG. 1( c) according to an example embodiment.

In the example embodiment, the cooling apparatus 100 is in the form of acircular disc comprising an upper face 110 and a lower face 120. Theupper face 110 of the cooling apparatus 100 is configured to receive aSolid Immersion Lens (SIL) (not shown). For example, as can be seen fromFIG. 1( a), a recess 102 comprising a substantially conical aperture 104is formed on the upper face 110 such that, during testing operation, theconical aperture 104 accommodates a corresponding conical portion of theSIL. In an alternate embodiment using an air-gap lens, the air-gap lensmay also be positioned directly above the conical aperture 104.

As can be seen from FIG. 1( d), the upper face 110, the lower face 120and a rim 130 of the cooling apparatus 100 together define a hollowchamber 140 capable of containing a cooling fluid (gas or liquid). Inthe example embodiment, an inlet 106 is provided on the top face 110 forinjecting the cooling fluid (gas or liquid), e.g. super-cooled air,water or diluted glycol, into the chamber 140, and an outlet 108 isprovided on the top face 110 diametrically opposite the inlet 106 forremoving said fluid from the chamber 140 during the cooling process,which will be described in detail below. The inlet 106 and outlet 108thus enable a continuous flow of cooling fluid in the exampleembodiment.

In addition, as can be seen from FIG. 1( b), an array of contactelements 112 (herein interchangeably referred to as contacts 112) aremounted adjacent the lower face 120. In the example embodiment, thecontact elements 112 are adjustable independently of one another, thusenabling a better surface contact with the target semiconductor device,such as a die, without requiring a high degree of planarity. Preferably,the contact elements 112 are fabricated using a heat conductingmaterial. In FIG. 1( b) the contact area of some of the contact elements112 are shown as hexagons. However, it should be appreciated that othershapes, e.g. triangle, square or polygon, may be used in alternateembodiments. Also, can be seen in FIGS. 1( b) and 1(d), the contacts 112in the central region of the lower face 120 have respective contactareas configured for maximizing contact with the semiconductor devicewithout covering the aperture 104 where the SIL lands, and foraccommodating the limited mounting space adjacent to the conicalaperture 104 in the chamber 140. In the example embodiment, this isachieved by using central contacts 112 with petal-shaped contact areasas shown in FIG. 1( b) and by positioning a mounting point of eachcentral contact 112 nearer to the respective outer end where more spaceis available (as illustrated in detail in FIG. 2( a)). Preferably, thisarrangement helps to achieve weight balance as the outer end istypically larger than the inner end.

FIG. 2( a) shows an enlarged view of detail B in FIG. 1( d). FIG. 2( b)shows an enlarged view of detail C in FIG. 1( d). In FIGS. 2( a)-(b),the same reference numerals are used to identify the same parts comparedto FIGS. 1( a)-(d).

The contact elements 112 a, 112 b are preferably mounted in aspring-loaded type configuration. In the example embodiment, thespring-loaded type configuration comprises anchoring the contactelements 112 a, 112 b on respective O-rings 202 a, 202 b disposedbetween the lower face 120 and respective bottom portions 203 a, 203 b.In the example embodiment, the O-rings 20 a, 202 b are fabricated froman elastic material such as rubber or silicone to provide spring loadingfor the contact elements 112 a, 112 b respectively. Thus, the array ofcontact elements 112 a, 112 b can advantageously conform to and maintaingood contact even with a die surface that does not have a high degree ofplanarity. Also, the contact elements 112 a, 112 b, which are typicallyfabricated from a thermally conductive material such as copper, arecoated with a relatively softer material such as gold at least on thecontact areas of the respective bottom portions 203 a, 203 b in theexample embodiment, for further enhancement of the thermal contact withthe surface of the die.

Also, in the example embodiment, top portions 205 a, 205 b of thecontact elements 112 a, 112 b are disposed within the chamber 140 suchthat, during operation, heat is conducted from the silicon substrate tothe contact elements 112 a, 112 b and is removed by direct contact withthe cooling fluid, e.g. super-cooled air, water or diluted glycol,present in the chamber 140. The contact elements 112 a, 112 b thusincrease the effective cooling surface of the silicon substrate duringoperation. In a preferred embodiment, the top portions 205 a, 205 b ofthe contact elements 112 a, 112 b are formed integrally with or aresecured to respective cooling fins 204 a, 204 b, which are also made ofa heat conducting material, to enhance the heat exchange with thecooling fluid in the chamber 140.

FIG. 3( a) shows a perspective view of a cooling apparatus 300 accordingto an alternate embodiment. FIG. 3( b) shows an alternative perspectiveview of the cooling apparatus 300 of FIG. 3( a). FIG. 3( c) shows a sideview of the cooling apparatus 300 of FIG. 3( a).

Similar to the cooling apparatus 100 described above with respect toFIG. 1, the cooling apparatus 300 in this embodiment is in the form of acircular disc comprising an upper face 310, a rim 330 and a lower face320. Fastening means, e.g. screws 314, are used to secure the upper face310 to the lower face 320. The upper face 310 of the cooling apparatus300 is configured to receive a Solid Immersion Lens (SIL) (not shown),e.g. by having a recess 302 comprising a substantially conical aperture304 formed on the upper face 310. During testing operation, the conicalaperture 304 can accommodate a corresponding conical portion of the SIL.In another embodiment using an air-gap lens, the air-gap lens may alsobe positioned directly above the conical aperture 304. Also, an inlet306 is provided for injecting the cooling fluid (gas or liquid), e.g.super-cooled air, water or diluted glycol, into a chamber (not shown inFIG. 1). The fluid that has been used for cooling is then removed via anoutlet 108 disposed diametrically opposite the inlet 106, such that theinlet 106 and outlet 108 enable a continuous flow of the cooling fluidacross the chamber in the example embodiment.

Further, an array of contact elements 312 (herein interchangeablyreferred to as contacts 312) are mounted adjacent the lower face 320. Inthe example embodiment, the contact elements 312 are adjustableindependently of one another, thus enabling a better surface contactwith the target semiconductor device, for example a die, withoutrequiring a high degree of planarity. Preferably, the contact elements312 are fabricated using a thermally conductive material such as copper,and may be coated with a relatively softer material such as gold atleast on the contact areas for further enhancement of the thermalcontact with the die. In FIG. 3( b) the contact area of some of thecontact elements 312 are shown as hexagons. However, it should beappreciated that other shapes, e.g. triangle, square or polygon, may beused in other embodiments.

FIG. 4( a) shows a cross-sectional view of the cooling apparatus 300 ofFIG. 3( a) according to an example embodiment. As can be seen from FIG.4( a), the upper face 310, the lower face 320 and a rim 330 of thecooling apparatus 300 together define a hollow chamber 340 forcontaining the cooling fluid, as described above. Preferably, the degreeof slant of the conical aperture 304 is adjustable, depending on e.g.the type of lens used. For example, the conical aperture 304 shown inFIG. 4( a) is more pointed compared to that shown in FIG. 2.

FIG. 4( b) shows an enlarged view of a center contact 410 in detail B ofFIG. 4( a). FIG. 4( c) shows an enlarged view of contact elements 312 indetail C of FIG. 4( a). As shown in FIG. 4( b), the center contact 410comprises a hollow center portion defining the conical aperture 304(FIG. 3( a)), recesses (to be shown in FIG. 5) to receive elasticO-rings 404, 406. The elastic O-rings 404, 406 provide tight fluid sealsbetween the center contact 410 and an upper plate 412 and lower plate402 respectively such that the cooling fluid may not leak from thechamber 340.

Referring now to FIG. 4( c), the contact elements 312 a, 312 b, 312 care arranged such that their respective bottom portions are in contactwith one another, while gaps exist between their respective top portionsto allow the cooling fluid to circulate within the chamber 340. In theexample embodiment, the top portion of each contact element 312 a, 312b, 312 c is substantially cylindrical and configured to have a biasingelement, here in the form of a spring 418 a, 418 b, 418 c to be mountedthereon. Each of the springs 418 a, 418 b, 418 c is biased against thetop plate 412 at one end, and against the bottom plate 402 at anotherend. This arrangement allows contact elements 312 a, 312 b, 312 c to bemounted in a spring-loaded type configuration in the example embodiment,such that the contact elements 312 a, 312 b, 312 c are adjustable duringoperation. Further, each contact element (e.g. 312 b) comprises a recessfor receiving a respective O-ring 414 b for establishing a fluid sealwith the bottom plate 402 such that the cooling fluid may not leak fromthe chamber 340.

As shown in FIG. 4, each of the center contact 410 and contact elements312 in the example embodiment is mounted by the respective spring andO-ring, allowing them to be adjustable independently of one another.Thus, in the example embodiment, the array of contact elements 312 a,312 b, 312 c can advantageously conform to and maintain good contacteven with a die surface that does not have a high degree of planarity.

FIG. 5( a) shows a perspective view of the center contact 410 of FIG. 4(b) according to an example embodiment. FIG. 5( b) shows a side view ofthe center contact 410 of FIG. 5( a). The center contact 410 comprisesan upper cylindrical portion 502 where the spring 408 (FIG. 4( b)) ismounted on, and a lower cylindrical portion 504 comprising a smallerdiameter than the upper cylindrical portion 502 for mounting to thelower plate 402 (FIG. 4( b)). A recess 508 is disposed on a top rim ofthe center contact 410 for receiving the O-ring 406 (FIG. 4( b)), whilea recess 506 is disposed on the lower cylindrical portion 504 forreceiving the O-ring 404 (FIG. 4( b)).

FIG. 6( a) shows a perspective view of the contact element 312 b of FIG.4( c) according to an example embodiment. FIG. 6( b) shows a side viewof the contact element 312 b of FIG. 6( a). The contact element 312 bcomprises a cylindrical upper portion 602 where the spring 418 (FIG. 4(c)) is mounted on, and a lower portion 604 defining e.g. a hexagonalcontact surface 614. Additionally, the contact element 312 b comprises arecess 606 for receiving the O-ring 414 b (FIG. 4( c)), and a recess 608for receiving, e.g. a clip to hold the contact element 312 b in a normalposition. During operation, the contact surface 614 contacts thesemiconductor device (not shown) and transfers the heat from thesemiconductor device to the upper portion 602, where the heat is removedby the cooling fluid. In a preferred embodiment, the upper portion 602comprises vertical grooves 610 for increasing a surface area in contactwith the cooling fluid, thereby enhancing the heat transfer from thecontact element 312 b to the cooling fluid.

FIG. 7 shows an exploded perspective view of a cooling apparatus 650according to another embodiment. A membrane or sheet 652 of highlythermal conductive and flexible material is placed between the array ofcontact elements 654 and the device or die to be tested (not shown). Inthis embodiment, the sheet 652 is attached to the face 656 of thecooling apparatus 650 using a plurality of screws e.g. 658 received incorresponding threaded holes e.g. 660 in the face 656. The material ofthe sheet 652 is preferably compressible and soft. The sheet 652 isdetachable and easily replaceable.

The thermally conductive sheet 652 advantageously (1) lowers the thermalcontact resistance between the contact elements 654 and the device ordie to be tested, and (2) conducts/spreads the heat radially outwardsbetween the contact elements 654. In other words, with the thermallyconductive sheet 652 installed, poorly-contacted contact elements and/orcontact elements landed on areas where less heat is being generatedand/or contact elements landed on areas with poor lateral thermalconductivity will nevertheless contribute and/or will have an increasedcontribution to conduct the heat away from the device or die.

As an example, a high thermally conductive and flexible material fromwhich the sheet 652 can be made from is graphite, pyrolytic graphite,indium or gold.

The sheet 652 can be held in place by the screws e.g. 658 and washerse.g. 662 on the circumference of the face 656. A through hole or throughopening 664 is preferably formed in the center of the sheet 652 tocoincide with, and of substantially the same size as, the aperture orthrough hole 666 in the chamber 668 for allowing inspection of thedevice or die by e.g. a solid immersion lens (SIL) or an air gap lens.In this embodiment, the cooling apparatus 650 comprises a bracketstructure 670 receiving the chamber 668, for mounting in a cooling andinspection system (not shown). The chamber 668 and array of contactelements 654 in this embodiments are essentially the same as in theembodiments described above with reference to FIGS. 1 to 6.

FIG. 8 shows an exploded perspective view of a system 800 for inspectinga packaged semiconductor device 811 such as a microprocessor packagedwith flip chip technology, according to an example embodiment. The die802 is typically inverted and provided on a package substrate 810together with die-side components 804, as will be appreciated by aperson skilled in the art. The packaged semiconductor device 811 isusually mounted in a socket (not shown) during testing. The coolingapparatus 100, 300, 650 is disposed between a solid immersion lens (SIL)assembly 820 and the packaged semiconductor device 811 such that theupper face of the cooling apparatus 100, 300, 650 is adjacent to the SILassembly 820, while the lower face of the cooling apparatus 100, 300,650 is adjacent to the backside of the die 802 in the exampleembodiment. Thus, the cooling apparatus 100, 300, 650 advantageouslyallows inspection and analysis of the die 802 through the siliconsubstrate (or backside) while removing heat generated by the die 802.FIG. 9( a) shows a perspective view of the system 800 of FIG. 8 when theSIL assembly 820 is in contact with the cooling apparatus 100, 300, 650.FIG. 9( b) shows a side view of the system 800 of FIG. 9( a). FIG. 9( c)shows a cross-sectional view of the system 800 of FIG. 9( a). As can beseen in e.g. FIG. 9( c), the conical aperture 104 of the coolingapparatus 100, 300, 650 receives a conical tip 822 of the SIL assembly820, e.g. during operation, for inspection of the packaged semiconductordevice (not shown).

As described above, the cooling apparatus in the example embodiments hasadvantageously provided improved thermal contact and conductivity suchthat the thermal resistance is advantageously reduced, thereby allowingthe user to operate the semiconductor device at a higher power.Preferably, the cooling apparatus in the example embodiments can coolthe semiconductor device to temperatures below 0° C. and does notrequire the surface of the silicon substrate to have high planarity. Forexample, the die may be polished prior to testing to remove at leastpart of the silicon substrate, and planarity requirements for suchpolishing can preferably be relaxed. Furthermore, after polishing, thesurface of the die is usually lower than the die-side components on thepackaged semiconductor device. The cooling apparatus can accommodate thenow taller die-side components and the die-side components,advantageously, do not need to be removed in the example embodiments.Also, since the cooling fluid is contained within the cooling apparatusrather than being sprayed onto the semiconductor device, the SILadvantageously does not need to have sealed optics in the exampleembodiments.

FIG. 10 shows a flow chart 1000 illustrating a method for cooling asemiconductor device according to an example embodiment. At step 1002, asurface of the semiconductor device is contacted with respective endportions of an array of contact elements thermally coupled to a coolingfluid. At step 1004, a flexible, heat conductive sheet is disposedbetween the respective end portions of the contact elements and thesurface of the semiconductor device for transferring heat generated inthe semiconductor device to the cooling fluid via the sheet and thecontact elements.

The method may comprise compressing the sheet to accommodate a profileof the surface of the semiconductor device for lowering the thermalcontact resistance between the respective ends of the contact elementsand the surface of the semiconductor device.

The method may comprise spreading heat between the contact elements viathe sheet for balancing respective heat transfer loads in the contactelements.

The method may comprise providing a through opening in the sheet andinspecting the semiconductor device by at least one of a solid immersionlens (SIL) and an air gap lens using the through opening.

The method may comprise securing the sheet to an external surface of achamber configured to receive the cooling fluid. The sheet may bedetachably secured to the external surface of the chamber forreplacement of the sheet. The sheet may be secured directly orindirectly to the external surface of the chamber.

The method may comprise configuring the sheet such that no bond isformed between the sheet and the respective ends of the contactelements.

The method may comprising configuring the sheet such that no bond isformed between the sheet and the surface of the semiconductor device.

The sheet may be made from any suitable material which providesflexibility and heat conduction, and may for example be made from one ormore of a group consisting of graphite, pyrolytic graphite, indium andgold.

In one embodiment, an apparatus for cooling a semiconductor devicecomprises a chamber configured for receiving a cooling fluid, an arrayof contact elements configured to be thermally coupled to the coolingfluid, and a flexible, heat conductive sheet disposed at respective endportions of the contact elements, such that, in operation, the sheet isdisposed between the respective end portions of the contact elements andthe surface of the semiconductor device for transferring heat generatedin the semiconductor device to the cooling fluid via the sheet and thecontact elements.

The sheet may be compressible for accommodating a profile of the surfaceof the semiconductor device such that, in operation, the thermal contactresistance between the respective ends of the contact elements and thesurface of the semiconductor device is lowered.

The sheet may be configured to spread heat between the contact elementsfor balancing respective heat transfer loads in the contact elements.

The sheet may comprise a through opening for allowing inspection of thesemiconductor device by at least one of a solid immersion lens (SIL) andan air gap lens.

The sheet may be secured to an external surface of the chamberconfigured to receive the cooling fluid. The sheet may be detachablysecured to the external surface of the chamber for replacement of thesheet. The sheet may be secured directly or indirectly to the externalsurface of the chamber.

The sheet may be configured such that, in operation, no bond is formedbetween the sheet and the respective ends of the contact elements.

The sheet may be configured such that, in operation, no bond is formedbetween the sheet and the surface of the semiconductor device.

The sheet may be made from any suitable material which providesflexibility and heat conduction, and may for example be made from one ormore of a group consisting of graphite, pyrolytic graphite, indium andgold.

It will be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

For example, it will be appreciated that the present invention is alsoapplicable to cooling devices other than those described in the exampleembodiments.

1. A method for cooling a semiconductor device, the method comprisingthe steps of: contacting a surface of the semiconductor device withrespective end portions of an array of contact elements thermallycoupled to a cooling fluid, disposing a flexible, heat conductive sheetbetween the respective end portions of the contact elements and thesurface of the semiconductor device such that the sheet extendscontinuously across the end portions of the contact elements fortransferring heat generated in the semiconductor device to the coolingfluid via the sheet and the contact elements, and detachably securingthe sheet to an external surface of a chamber configured to receive thecooling liquid, so as to enable the replacement of the sheet.
 2. Themethod as claimed in claim 1, comprising compressing the sheet toaccommodate a profile of the surface of the semiconductor device forlowering the thermal contact resistance between the respective ends ofthe contact elements and the surface of the semiconductor device.
 3. Themethod as claimed in claim 1, comprising spreading heat among thecontact elements via the sheet for balancing respective heat transferloads in the contact elements.
 4. The method as claimed in claim 1,comprising providing a through opening in the sheet and inspecting thesemiconductor device by at least one of a solid immersion lens (SIL) andan air gap lens using the through opening.
 5. (canceled)
 6. (canceled)7. The method as claimed in claim 1, comprising configuring the sheetsuch that no bond is formed between the sheet and the respective ends ofthe contact elements.
 8. The method as claimed in claim 1, comprisingconfiguring the sheet such that no bond is formed between the sheet andthe surface of the semiconductor device.
 9. The method as claimed inclaim 1, wherein the sheet is made from one or more of a groupconsisting of graphite, pyrolytic graphite, and gold.
 10. An apparatusfor cooling a semiconductor device, comprising: a chamber configured forreceiving a cooling fluid, an array of contact elements configured to bethermally coupled to the cooling fluid, and a flexible, heat conductivesheet disposed at respective end portions of the contact elements, suchthat, in operation, the sheet is disposed between the respective endportions of the contact elements and the surface of the semiconductordevice such that the sheet extends continuously across the end portionsof the contact elements for transferring heat generated in thesemiconductor device to the cooling fluid via the sheet and the contactelements, wherein the sheet is detachably secured to an external surfaceof a chamber configured to receive the cooling liquid, so as to enablethe replacement of the sheet.
 11. The apparatus as claimed in claim 10,wherein the sheet is compressible for accommodating a profile of thesurface of the semiconductor device such that, in operation, the thermalcontact resistance between the respective ends of the contact elementsand the surface of the semiconductor device is lowered.
 12. Theapparatus as claimed in claim 10, wherein the sheet is configured tospread heat among the contact elements for balancing respective heattransfer loads in the contact elements.
 13. The apparatus as claimed inclaim 10, wherein the sheet comprises a through opening for allowinginspection of the semiconductor device by at least one of a solidimmersion lens (SIL) and an air gap lens.
 14. (canceled)
 15. (canceled)16. The apparatus as claimed in claim 10, wherein the sheet isconfigured such that, in operation, no bond is formed between the sheetand the respective ends of the contact elements.
 17. The apparatus asclaimed in claim 10, wherein the sheet is configured such that, inoperation, no bond is formed between the sheet and the surface of thesemiconductor device.
 18. The apparatus as claimed in claim 10, whereinthe sheet is made from one or more of a group consisting of graphite,pyrolytic graphite, indium and gold.
 19. (canceled)